[owlmonkey]

One study says ~38 individual base mutations per generation, but that increases by about 2 bases per year of the father's age, which is still not much given 6 billion base pairs in humans. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548427/) These studies, however, are missing rearrangements and other spontaneous structural changes which might not modify the genes at all but might change their expression or dosage. We don't have enough data yet about structural mutation rates, the technology to assess that at scale and low cost is only coming online now. Not sure about the incident rate, but since the guidelines for reporting have widened so much in the last decade that might mask any ability to really know.